This invention relates to a process for producing propylene oligomers (The meaning of this "Oligomer" contains "dimer" and "telomer".) used, for example, as starting materials for polymers, base materials for preparing lubricating oils and starting materials for various chemical products. More particularly, it relates to a process for producing propylene oligomers having mainly a polymerization degree of 2-10 and having a vinyl group at terminal of molecule at a high selectivity.
It is known that Ziegler-Natta catalyst is used for production of propylene oligomers in addition to solid catalysts containing alkali metals. Typically, it has been known to polymerize propylene using catalysts comprising combination of nickel compound and aluminum compound or catalysts comprising titanium compound and organoaluminum compound, or sodium-potassium catalysts.
However, products obtained by these processes are mixtures of various components such as polymers having vinyl group at molecular terminal, various internal olefins such as dimers, e.g., 2-methylpentene-2,4-methylpentene-2,2,3-dimethylbutene-2, hexene-2, etc., vinylidene compounds such as dimers, e.g., 2-methylpentene-1,2,3-dimethylbutene-1, etc. Therefore, complicated separating operations are necessary for obtaining industrially useful propylene oligomers having vinyl group at molecular terminal. There is another problem that selectivity per se of the propylene oligomers having vinly group at molecular terminal is low.